The present invention relates to processes for manufacturing hydraulic anti-vibration mounts designed to be inserted, for damping and connecting purposes, between two rigid elements such as an engine and the bodywork of a vehicle. It also relates to the mounts produced by these processes.
Of these mounts, the invention relates more particularly to those which comprise:
a first rigid part and a second rigid part, each attachable to one of the two rigid elements to be connected together,
an elastomeric body for connecting together the two rigid parts and partially defining a liquid-filled working chamber,
a compensating chamber defined partially by a flexible, easily deformable wall,
a rigid partition for separating the working chamber from the compensating chamber while defining a restricted passage allowing communication between the said chambers, the rigid partition comprising a rigid recessed shell having first and second faces, the first face of the rigid shell being oriented toward one of the two chambers, termed the first chamber, while the second face of the rigid partition is oriented toward the other of the two chambers, termed the second chamber.
A hydraulic anti-vibration mount such as this is disclosed for example in document FR 2 593 868.
These hydraulic anti-vibration mounts of the prior art are perfectly satisfactory and are very efficient at damping particularly relatively large-amplitude vibrations of relatively low frequency such as those due to the jolting caused in the vehicle by bumps in the road. In particular, the efficiency of these anti-vibration mounts is at is greatest for vibrations of a frequency corresponding to the resonance of the column of liquid contained in the restricted passage, which frequency depends on the geometrical dimensions of the said restricted passage and specifically on the ratio of the curvilinear length to.the equivalent diameter of this restricted passage.
This aspect means, however, that a greater number of types of product have to be produced, notably the types of rigid partition in which the restricted passage is defined, when it is desired to modify the set frequency of the anti-vibration mount, for example between two models of the same vehicle. This lack of standardization increases the cost price of the anti-vibration mount.
It is a particular object of the present invention to reduce this problem.
To this end, the invention provides a process for manufacturing hydraulic anti-vibration mounts belonging to at least a first group and a second group of mounts exhibiting a first and a second set frequency, respectively, and being designed to be inserted between two rigid elements that are to be connected together, this process comprising the operations of supplying and assembling:
a first rigid part and a second rigid part, each attachable to one of the two rigid elements to be connected together,
an elastomeric body for connecting together the two rigid parts and partially defining a liquid-filled working chamber,
a compensating chamber defined partially by a flexible, easily deformable wall,
a rigid partition for separating the working chamber from the compensating chamber while defining a restricted passage allowing communication between the said chambers, the rigid partition comprising a rigid recessed shell having first and second faces, the first face of the rigid shell being oriented toward one of the two chambers, termed the first chamber, while the second face of the rigid partition is oriented toward the other of the two chambers, termed the second chamber,
this process being characterized in that it comprises the following steps:
a) manufacturing a plurality of rigid shells, all identical with each other, with a first groove and a second groove independent of the first groove, the said grooves being recessed in the first face of the rigid partition and communicating with the first chamber and with the second chamber through at least one opening formed in the rigid shell,
b) manufacturing a plurality of closing plates designed to fit more or less leaktightly against the first face of the rigid shells in such a way as to cover the first and second grooves, in order at least partially to define the restricted passage, the closing plates being divided into at least a first group and a second group, the closing plates of the first group having a cavity located over the first groove of the rigid shells and having only a solid part over the second groove of the rigid shells, thus isolating this second groove, and, the closing plates of the second groove each having a cavity that is located over at least the second groove of the rigid shells,
c) producing a first group of anti-vibration mounts by attaching the rigid shells to the closing plates of the first group, and a second group of anti-vibration mounts by attaching the rigid shells to the closing plates of the second group.
With these arrangements it is possible to standardize the manufacture of the rigid shell forming the essential element of the partition between the working and compensating chambers: in order to modify the set frequency of a given anti-vibration mount, e.g. to adapt it to a different engine in the same vehicle, only the closing plate of the rigid shell has to be modified in such a way that the closing plate allows communication between the first chamber and either the first groove only, or both the first and second grooves, or perhaps the second groove only if the latter is of different dimensions to the first groove.
Preferred embodiments of the invention may also, if required, make use of one or more of the following arrangements:
the closing plates of the second group each comprise a cavity that is located over the first and second grooves of the rigid shells;
gratings are formed, one in the rigid shell and the other in the closing plate;
there is formed in the rigid shell a central housing that communicates with the first and second chambers, via the gratings;
first and second grooves are formed so as to be concentric about the central housing;
a flexible decoupling valve is placed in the central housing;
the second groove communicates with the first chamber through the closing plate, the first and second grooves together at least partially forming the restricted passage;
the cavity of the closing plate that allows communication between the first groove and the first chamber, also allows communication between the second groove and the said first chamber;
the first and second grooves communicate with the second chamber via the said opening;
the first chamber consists of the working chamber and the second chamber consists of the compensating chamber;
the elastomeric body is shaped like a bell extending between a top integral with the first rigid part and an annular base integral with the second rigid part, the said annular base of the elastomeric body being attached leaktightly against a periphery of the closing plate of the rigid partition;
the first and second grooves run essentially parallel with each other on the first face of the rigid shell, the said grooves running between respective first ends, located in a solid portion of the rigid partition, and respective second ends communicating with the second chamber, the two grooves being separated from each other by a solid and continuous partition that joins the said solid part toward the first ends of the two grooves, and that runs as far as the second ends of the said two grooves, the said partition being in more or less leaktight contact with the closing plate between the first and second ends of the two grooves; and
the rigid shell also includes a central housing containing a flexible decoupling valve that communicates with the first and second chambers via gratings formed respectively in the rigid shell and in the closing plate, the first and second grooves being arranged concentrically around the valve housing.